Polarized photon measurements of the 12C(γ,pp) and 12C(γ,pn) reactions for Eγ=160350 MeV

C. J. Y. Powrie, J. C. McGeorge, I. J. D. MacGregor, J. Ahrens, J. R. M. Annand, J. F. Arneil, R. Beck, D. Branford, S. Franczuk, D. I. Glazier, P. Grabmayr, S. J. Hall, T. Hehl, P. D. Harty, D. G. Ireland, J. D. Kellie, K. Livingston, F. A. Natter, S. Oberkirsch, R. O. Owens, J. Ryckebusch, M. Sauer, A. Settele, and D. P. Watts
Phys. Rev. C 64, 034602 – Published 1 August 2001
PDFExport Citation

Abstract

The 12C(γ,pp) and 12C(γ,pn) reactions have been studied for Eγ=160350 MeV using linearly polarized photons from the Glasgow tagged photon spectrometer at the Mainz microtron MAMI. Both reaction channels show a negative photon asymmetry Σ for missing energies Em below 70 MeV, where direct emission nucleon pairs is expected. A strong peak at low Em is observed in Σ(γ,pp), but not in Σ(γ,pn). Further differences between the two reaction channels are observed in the Eγ dependence of Σ and in the angular distributions of differential cross sections for photons polarized parallel, or perpendicular, to the reaction plane. Theoretical calculations using an unfactorized distorted wave treatment of direct two-nucleon emission do not agree with the magnitude of the photon asymmetry or the angular dependence of the differential cross sections for either channel. For Em>70 MeV and Eγ>250 MeV, Σ has a substantial negative value which is similar for both reaction channels. This is attributed to two-step reactions following initial quasifree pion production.

  • Received 6 April 2001

DOI:https://doi.org/10.1103/PhysRevC.64.034602

©2001 American Physical Society

Authors & Affiliations

C. J. Y. Powrie1, J. C. McGeorge1, I. J. D. MacGregor1, J. Ahrens4, J. R. M. Annand1, J. F. Arneil2, R. Beck4, D. Branford1, S. Franczuk1, D. I. Glazier1, P. Grabmayr1, S. J. Hall1, T. Hehl3, P. D. Harty1, D. G. Ireland1, J. D. Kellie1, K. Livingston1, F. A. Natter3, S. Oberkirsch3, R. O. Owens1, J. Ryckebusch5, M. Sauer3, A. Settele3, and D. P. Watts1

  • 1Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom
  • 2Department of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
  • 3Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany
  • 4Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany
  • 5Department of Subatomic and Radiation Physics, University of Gent, Proeftunistraat 86, B-9000 Gent, Belgium

References (Subscription Required)

Click to Expand
Issue

Vol. 64, Iss. 3 — September 2001

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review C

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×